The function of vinegar in the cleaning run

[00Buck]

Hey yall. Been distilling a long while but only knew what I learned from the older folks before me. I never knew a thing about a vinegar run for cleaning a new rig or new parts until recently. So the question is what does the vinegar run itself do? Does the alcohol run itself not do the bulk of the cleaning and sanitizing?

Say for example you have a still youve been running already and you solder a new part to it, say a new elbow. Why cant you just run alcohol through it to clean? What does the vinegar do to help?